-LRB- CNN -RRB- -- The former stepson of singer Usher Raymond remained in critical condition in an Atlanta hospital Tuesday , four days after he was injured while riding in an inner tube at a north Georgia lake , his family said .

A personal water craft crashed into Kile Glover , 11 , and a girl as they rode on an inner tube that was being towed by a pontoon boat in Lake Lanier on Friday , according to an accident report from the Georgia Department of Natural Resources .

Kile suffered a serious head injury and was flown by helicopter to Children 's Healthcare at Egleston Hospital in Atlanta , it said .

The 15-year-old girl , who was not identified in the report , was also taken to the hospital . Her condition was not made public .

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Jeffrey Hubbard , a 38-year-old Atlanta man , was driving the personal water craft , the investigation report said . Investigators concluded that alcohol was not involved in the incident .

The family has held vigil at the hospital since Friday . Usher visited Kile early Saturday morning , but has not returned , according to a source close to the family .

`` We know God 's in control , and are leaning on our faith in Him and His word at this most difficult time , '' his family said in a statement to CNN Tuesday . `` We firmly believe in the power of prayer and ask that you all continue to pray and lift Kile up , as it 's the best way we can all support him now . ''

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Kile 's mother is Tameka Raymond , who was married to Usher for two years until their divorce in 2009 . The couple have two sons together , ages 3 and 4 .

Kile 's father is Ryan Glover , the president of Bounce TV , a fledgling television network targeting African-American audiences . He is also a former executive with Turner Broadcasting , the parent company of CNN .

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CNN 's Dave Alsup contributed to this report .

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Kile Glover , 11 , suffered a serious head injury when a jet ski hit him Friday

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Usher was married to Kile 's mother and is the father of his two young brothers

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`` We know God 's in control , '' Kile 's family says

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The child 's father is Bounce TV President Ryan Glover